1. Field of the Invention
The present invention generally relates to an optical signal transmission apparatus and method, and more particularly, to an optical signal transmission apparatus and method in which a greater safety is ensured.
In an optical transmission system, in general, optical signals whose optical wavelengths are nearly 1.5 .mu.m or 1.3 .mu.m are used. At these wavelengths, a transmission loss of an optical cable is minimum. Since these optical signals are not visible rays, it is difficult for a maintenance worker to discriminate whether or not an optical signal is being transmitted through the optical cable. Therefore, a conventional optical transmission apparatus is constructed such that it permits the optical cable to be disconnected only when a power supply is turned off. However, when a breaking down of the optical cable is caused, the optical signal is emitted from a disconnected section to the air. As a result, there is a problem that neighboring humans and animals may be in danger of, for example, losing of their eyesight.
2. Description of the Prior Art
FIG. 1 shows a configuration of the conventional optical transmission apparatus. The apparatus is constructed with a housing 100, a power supply section 101, an optical signal operating section 102 consisting of an optical signal transmission section 103 and a connection part 104, an optical cable 105, and a power supply connector 106.
In the apparatus, the power supply section 101 and the optical signal operating section 102 are located within the housing 100, and the power supply section 101 is connected with the optical signal operating section 102 by the power supply connector 106. From the power supply section 101, operating power is supplied to the optical signal operating section 102 through the power supply connector 106. Thereby, an optical signal is emitted from a luminous device of a semiconductor laser, etc., in the optical signal transmission section 103, and is transmitted to the optical cable 105 through the connection part 104.
In this configuration, when connecting and disconnecting the optical cable 105 to and from the optical signal transmission section 103 by the connection part 104, the connecting and disconnecting operations cannot be performed if the optical signal operating section 102 is not pulled out from the housing 100. In this case, when the optical signal operating section 102 is pulled out from the housing 100, the power supply connector 106 is disconnected, and the power from the power supply section 101 stops being supplied to the optical signal operating section 102. Therefore, light emission from the luminous device in the optical signal transmission section 103 stops completely. In this condition, the connecting and disconnecting operations for the optical cable 105 can be performed. After these operations are finished, when putting the optical signal operating section 102 into the housing 100, the optical signal operating section 102 is connected with the power supply section 101 through the power supply connector 106, and the light emission of the luminous device in the optical signal transmission section 103 is permitted. In the above manner, the maintenance worker is prevented from being in danger.
As mentioned above, in the conventional optical signal transmission apparatus, when connecting and disconnecting the optical cable 105, the optical signal operating section 102 is automatically disconnected from the power supply section 101 to stop the light emission during the maintenance. However, after the maintenance is finished, the optical signal is emitted regardless of a maintenance condition for the opposite optical signal transmission apparatus in the opposite station. There is a problem that a maintenance worker in the opposite station may be in danger. Further, the breaking down of the optical cable 105 may be caused, and the optical signal may be radiated from the disconnected section to the air. Since, this optical signal is not a visible ray, it is very difficult to discriminate the radiated optical signal in the air. Therefore, even if the power of the optical signal is small, for example, several mW, the intensity of the optical signal is very strong since the optical signal is the laser light. Therefore, people or animals may be in danger of losing their eyesight, etc., due to their retinas being effected by the optical signal.